A flexible multichannel cardiac mapping electrode for cardiac transport and its construction method

Abstract

This invention relates to the field of medical surgical instruments, specifically to a flexible multi-channel cardiac mapping electrode for cardiac transport and its construction method. The mapping electrode includes a flexible substrate, multiple electrodes, and an encapsulation layer. The flexible substrate has multiple branches, with the fixed ends of all branches connected to a common part. Multiple electrode arrays are disposed on the side of each branch that contacts the heart for measuring the cardiac potential. The flexible substrate is made of a biocompatible flexible insulating material, allowing each branch to be adsorbed by the surface tension of the body fluid on the outer surface of the heart. This not only reduces stimulation and damage to cardiac tissue but also allows the electrodes to more precisely conform to the heart surface, accurately measuring the cardiac potential and greatly improving the accuracy of cardiac electrical activity mapping.

Description

Technical Field

[0001] This invention relates to the field of medical surgical instruments, specifically to a flexible multi-channel cardiac mapping electrode for cardiac transport and its construction method. Background Technology

[0002] During heart transplantation, due to the difficulty in matching donor and recipient blood, it is often impossible for them to be in the same hospital. Therefore, the donor heart needs to be rapidly transported to the recipient's hospital, requiring the heart to be placed in specialized transport equipment. Currently, in heart transport, electrophysiological mapping of the heart is typically performed during donor heart retrieval (before retrieval) using ECG signals or electrophysiological mapping to determine the donor heart's condition, and then again before implantation into the recipient to determine the physiological state of the transplanted heart. This undoubtedly increases the time the heart remains outside the body, raising the risk of cardiac damage.

[0003] There are various existing methods for electrophysiological mapping of the heart's physiological state. Currently, commonly used electrophysiological mapping catheters involve inserting a multi-electrode mapping catheter into the heart. Each electrode contacts a different part of the heart, measuring electrical signals at different locations to determine the heart's state. For example, prior art CN 111436928 B discloses a high-precision multi-polar mapping electrode catheter with a rake-shaped tip. The catheter's end has 2-8 branch tubes, each with multiple ring electrodes. The lumen of each branch tube contains a shaping wire made of nickel-titanium alloy, which has a memory function and can quickly return to its original shape after the external force is removed. For example, CN117752404 B discloses a cardiac electrophysiological mapping and ablation catheter, which uses a sheet-like tip made of thermoplastic elastic material or shape memory alloy, and sets an electrode array on the sheet-like tip. By placing the sheet-like tip inside the heart, electrophysiological mapping and ablation treatment can be performed. The thermoplastic elastic material or shape memory alloy can make the sheet-like electrode fit the heart, thereby ensuring good contact between the electrode and the heart.

[0004] The aforementioned existing technologies all utilize shape memory alloys to ensure the electrodes adhere to the heart, thereby guaranteeing accurate measurement of electrical signals from cardiomyocytes. However, the shape memory effect of these alloys is temperature-triggered, remaining relatively soft at room temperature for easy delivery via vascular sheaths. Once inside the body, they return to their preset shape at body temperature. During transport of an ex vivo heart, to reduce cell metabolism and prolong survival time, it must be immersed in a cryoprotectant solution (such as UW or HTK solution) at approximately 4°C and transported in an ice bucket. This temperature is far below the shape transition temperature of the shape memory alloy, preventing the mapping catheter from unfolding into its preset functional shape. It remains in a soft, relaxed delivery state, unable to form stable and reliable contact with the heart wall, thus failing to acquire accurate and continuous electrical signals. Furthermore, vibration and shaking are inevitable during transport. A soft catheter that fails to unfold properly will have its electrodes slide on the heart surface, generating significant electrical noise that renders the signal unreadable. Additionally, the mapping catheter's inherent rigidity can scratch or even puncture fragile myocardial tissue during shaking, causing unnecessary damage. Therefore, currently available mapping catheters are unsuitable for cardiac transport. Summary of the Invention

[0005] To address the technical problem that existing technologies cannot perform real-time electrophysiological mapping of the heart during transport, this application provides a flexible multi-channel cardiac mapping electrode for cardiac transport and a method for its construction, wherein the mapping electrode includes:

[0006] A flexible substrate having multiple branches, with the fixed ends of all branches connected to a common portion, the flexible substrate being made of a biocompatible flexible insulating material, so that each branch can be adsorbed by the surface tension of bodily fluids on the outer surface of the heart;

[0007] Multiple electrodes are arrayed on the side of each branch that contacts the heart to measure the heart's potential. Each electrode is provided with an electrode wire that penetrates the flexible substrate and extends along the side of the flexible substrate away from the measuring electrode to the common part, and finally connects to the communication interface.

[0008] An encapsulation layer is disposed on the side of a flexible substrate facing away from the electrode and covers the electrode wires for encapsulating the electrode wires.

[0009] This application also provides a method for constructing a calibration electrode, comprising the following steps:

[0010] Acquire image data of the heart and build a three-dimensional model of the heart at the end of contraction;

[0011] Specify at least one electrode location on the three-dimensional model of the heart;

[0012] Based on the electrode positions, electrode wires and flexible substrates are designed to form a three-dimensional model of the calibration electrode.

[0013] The three-dimensional model of the calibration electrode is unfolded into a two-dimensional planar graphic to form an electrode pattern;

[0014] The calibration electrode is prepared according to the electrode pattern.

[0015] The technical effects and advantages of this invention are as follows: Using a biocompatible flexible insulating material as a flexible substrate, the branches adhere to the heart by leveraging the surface tension of the fluid on the outer surface of the heart. This not only reduces stimulation and damage to cardiac tissue but also allows the electrodes to more precisely conform to the heart surface, accurately measuring cardiac potentials and significantly improving the accuracy of cardiac electrophysiological mapping. Furthermore, by acquiring cardiac image data to establish a three-dimensional model of the heart at the end of contraction, and specifying electrode positions on this model, a three-dimensional model of the mapping electrodes is created based on these positions. Mapping electrodes are then fabricated based on this model, enabling personalized electrode design according to the patient's specific cardiac morphology and characteristics. This improves the fit between the mapping electrodes and the heart, further enhancing the accuracy of the acquired electrophysiological signals. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the calibration electrode provided in Embodiment 1 of the present invention.

[0017] Figure 2 For the present invention Figure 1 Sectional view of section AA.

[0018] Figure 3 For the present invention Figure 1 BB section sectional view.

[0019] Figure 4 This is a plan view of the unfolded calibration electrode of the present invention.

[0020] Figure 5 This is a flowchart of the method for constructing the calibration electrode according to the present invention.

[0021] Figure 6 This is a flowchart of the process for selecting candidate calculation images in the method for constructing the calibration electrode of the present invention.

[0022] Figure 7 This is a schematic diagram of the tree-like structure of the electrode wires established by the calibration electrode construction method of the present invention.

[0023] Figure 8 This is a schematic diagram of the overall structure of the calibration electrode provided in Embodiment 2 of the present invention.

[0024] Figure 9This is a simplified diagram showing the force calculation of the mapping electrode provided in Embodiment 2 of the present invention during cardiac diastole.

[0025] Figure 10 This is a flowchart illustrating the optimization of the three-dimensional model of the calibration electrode in the calibration electrode construction method of the present invention.

[0026] Figure 11 This is a plan view of the calibration electrode after it has been unfolded, as provided in Embodiment 3 of the present invention.

[0027] Figure 12 For the present invention Figure 11 The CC section view in the image.

[0028] The reference numerals in the attached figures are as follows: 1. Flexible substrate; 11. Branch; 12. Common part; 13. Bus part; 14. Annular fastening part; 15. Connecting hole; 16. Connecting pin; 161. Disc head; 162. Fixing pin; 17. Connecting part; 18. Fastening pull ring; 2. Electrode; 21. Electrode wire; 3. Encapsulation layer; 4. Communication interface. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] refer to Figures 1 to 4 Embodiment 1 of the present invention provides a flexible multi-channel cardiac mapping electrode for cardiac transport, comprising:

[0032] The flexible substrate 1 has multiple branches 11, each branch 11 having a free end at one end and a fixed end at the other, with the fixed ends of all branches 11 connected to a common part 12. The entire flexible substrate 1 is made of a biocompatible flexible insulating material, with a thickness controlled between 5-200 μm, and the width of each branch 11 controlled between 100 μm and 3 cm, so that each branch 11 can be adsorbed by the surface tension of the body fluid on the outer surface of the heart.

[0033] Multiple electrodes 2 are arrayed on the side of each branch 11 that contacts the heart, for measuring the heart's potential. Each electrode 2 is provided with an electrode wire 21 that penetrates a flexible substrate 1 (e.g., Figure 2 and Figure 3As shown in the figure, it extends along the side of the flexible substrate 1 away from the measuring electrode 2 to the common part 12, and finally connects to the communication interface 4 through the bus part 13. The thickness of the electrode 2 and the electrode wire 21 is controlled between 10-300μm, the width of the electrode wire 21 is controlled between 10-300μm, and the spacing between two adjacent electrode wires 21 is 200μm-2cm. It is necessary to ensure the conductivity of the electrode wire 21, while also requiring it to have sufficient flexibility.

[0034] The encapsulation layer 3, whose shape is adapted to the flexible substrate 1, is disposed on the side of the flexible substrate 1 facing away from the electrode 2 and covers the electrode wires 21. It is used to encapsulate the electrode wires 21 and prevent body fluid from connecting the various electrode wires 21 and generating noise. The material and thickness of the encapsulation layer 3 are the same as those of the flexible substrate 1, thereby giving the entire calibration electrode sufficient flexibility.

[0035] The flexible substrate 1 can be made of PI (polyimide) film, PDMS (polydimethylsiloxane), or PU (polyurethane) film. Both possess excellent biocompatibility and flexibility, allowing them to conform well to the irregular shape of the heart's outer surface and reduce interference with normal cardiac physiological activities. PI film exhibits high mechanical strength and chemical stability, maintaining structural integrity during long-term contact with body fluids and resisting deformation or damage, ensuring the long-term stable operation of electrode 2. PDMS, on the other hand, has good elasticity and low surface energy, better adapting to the dynamic movement of the heart and less prone to adsorbing surrounding biomolecules, reducing the risk of biocontamination.

[0036] In practical applications, PDMS is preferred, and the side of the flexible substrate 1 that is attached to the heart undergoes a hydrophilic treatment. This can be achieved by coating it with hydrophilic polymers such as PVA (polyvinyl alcohol) and curing it with heat to form a stable coating, or by using plasma cleaning to form silanol (Si-OH) groups on the surface. This hydrophilic treatment allows the flexible substrate to better adhere to surfaces containing liquids. Simultaneously, its excellent elasticity reduces pressure on the heart, ensuring effective contact between the electrode 2 and the heart. PDMS has an elastic modulus of 0.4-2 MPa, far lower than PI (2.5-8 GPa), exhibiting superior tensile strength. The substrate can be stretched to 2-3 times its own length without breaking, which is highly effective in adapting to the heart's beating. Furthermore, the transparent PDMS electrode 2 allows researchers to directly observe the contact between the electrode 2 and the tissue while recording electrical signals, thus promptly identifying potential contact problems.

[0037] Gold or platinum are commonly used materials for conductors. However, these materials have poor tensile properties, which limits the tensile characteristics of branch 11 when applied to the measuring electrode. Therefore, conductive silver paste, platinum carbon, PEDOTPSS, etc. can be used for electrode conductors 21. These materials not only have excellent conductivity but also good tensile deformation ability. In particular, PEDOTPSS can maintain its conductivity without significant change as branch 11 is stretched, making it suitable as the material for electrode conductors 21 disclosed in this application.

[0038] Depending on the material of the flexible substrate 1, different fabrication processes are required. For example, when using PI thin film to fabricate the flexible substrate 1, MEMS (micro-nano lithography) technology can be used. When using PDMS to fabricate the flexible substrate 1, screen printing is preferred because it is simpler and less expensive.

[0039] Based on screen printing technology, using PDMS as the material for the flexible substrate 1 and the encapsulation layer 3, and PEDOTPSS as the material for the electrode wire 21, the method for constructing the calibration electrode provided in this application is as follows:

[0040] 1. Establish a three-dimensional model of the heart;

[0041] 2. Specify at least one electrode 2 on the three-dimensional model of the heart;

[0042] 3. Arrange electrode wires 21 according to the position of each electrode 2 to form an electrode pattern, and prepare an electrode mesh according to the electrode pattern;

[0043] 4. Form a flexible substrate pattern based on the electrode pattern, and prepare the substrate stencil and the encapsulation layer stencil;

[0044] 5. The flexible substrate 1, electrode 2, electrode wire 21, and encapsulation layer 3 are printed sequentially using the substrate stencil, electrode stencil, and encapsulation layer stencil.

[0045] 6. After drying, weld or connect the communication interface 4 to the common part 12 to complete the preparation of the calibration electrode.

[0046] Figure 4 The prepared calibration electrode is in its unfolded state.

[0047] In the above preparation process, in order to make the prepared mapping electrode 2 adaptable to the size and shape of the heart and ensure that the contact pressure between each electrode and the heart is similar, the electrode pattern is obtained through the following steps:

[0048] S1. Acquire image data of the heart and establish a three-dimensional model of the heart at the end of contraction;

[0049] S2. Specify at least one electrode 2 on the three-dimensional model of the heart;

[0050] S3. Design the shape of the electrode wire 21 and the flexible substrate 1 according to the position of each electrode 2 to form a three-dimensional model of the calibration electrode.

[0051] S4. Unfold the three-dimensional model of the calibration electrode into a two-dimensional planar graphic to form an electrode pattern.

[0052] To ensure that the mapping electrode maintains good contact with the heart throughout the heartbeat, the shape and size of the mapping electrode 2 should be adapted to the smallest possible state of the heart. When the heart dilates and expands, the flexibility of the mapping electrode 2 allows it to change with the heartbeat, thus ensuring a close fit to the heart.

[0053] Specifically, in step S1, the three-dimensional model of the heart at the end of contraction can be used to build a dynamic three-dimensional model of the heart based on the image data, and then the model of the heart at the end of contraction can be obtained based on the dynamic three-dimensional model. However, such modeling work is too much and requires processing of all image data.

[0054] Therefore, when acquiring cardiac image data, the heart's physiological electrical signals are acquired simultaneously. The image data is then filtered based on these signals, retaining only the images taken at the end of contraction. This data is then used to build a 3D model of the heart, thereby reducing data processing volume and improving modeling efficiency. (See the attached reference for details.) Figure 5 This includes the following steps:

[0055] S11. Simultaneously acquire cardiac image data and physiological electrical signals;

[0056] S12. Based on the physiological electrical signals, peak and valley values ​​are selected to identify the heart's pulsation cycle, and image data of the heart in the contraction state are selected as candidate images for calculation.

[0057] S13. Use deep learning algorithms to segment and register candidate computational images to establish a three-dimensional model of the heart.

[0058] Specifically, in step S11, the physiological electrical signal can be either an ECG signal or a cardiac electrophysiological mapping signal measured through the mapping catheter and electrode 2; both can be used to identify the heart's beating cycle. The image data can be either CT scan image information or MRI image.

[0059] For ECG signals, ventricular contraction ends near the end of the T wave, at which point the ventricular volume is at its smallest, typically occurring moment immediately after the T wave ends. Therefore, when selecting candidate images for computation, the T wave in the ECG signal can be used as a basis for selection, referencing... Figure 6 Specifically, it includes the following steps:

[0060] S121. Identify the RR interval in the physiological electrical signal. For each RR interval, define a T wave search window after the R wave.

[0061] There are several methods for identifying the R-R interval, a common one being threshold-based detection. This method sets an appropriate threshold; when the physiological electrical signal exceeds this threshold, an R wave is considered detected, thus determining the R-R interval. This method is relatively simple to implement and requires less computation, but it has high requirements for signal quality. If the signal is subject to noise interference, it may lead to misjudgment.

[0062] Another method is template matching. This involves first constructing a standard R-wave template, then sliding the template across the physiological electrical signal for matching. The position of the R-wave is determined by calculating the similarity, thus obtaining the R-R interval. This method is highly adaptable to different signals and can overcome the influence of noise to some extent. However, template construction requires a large amount of sample data, and the computational complexity is relatively high.

[0063] In addition, wavelet transform-based methods are also commonly used. Wavelet transform features multi-resolution analysis, enabling the decomposition of signals into different scales. By analyzing signal characteristics at different scales, the R-wave can be accurately identified, thereby determining the R-R interval. This method provides relatively accurate analysis of the time-frequency characteristics of signals and can effectively handle complex signals; however, the algorithm is relatively complex to implement and computationally intensive.

[0064] Different identification methods have their own advantages and disadvantages. In practical applications, it is necessary to select the appropriate method according to the specific signal characteristics and application scenarios to ensure the accuracy and reliability of R-R interval identification, and to provide accurate basic data for subsequent screening of candidate images based on the T wave in the ECG signal.

[0065] S122. Search for peak points other than the R peak during the RR interval as candidate points for the T wave;

[0066] There are many methods for searching peak values, mainly including threshold search and derivative search.

[0067] Threshold search involves setting a suitable threshold; when a signal value exceeds this threshold, the corresponding point is marked as a potential peak. This method is simple, straightforward, and computationally inexpensive, quickly filtering out a batch of potential peak candidates from the signal. However, its drawback lies in the criticality of the threshold setting. If the threshold is set too high, some true peaks may be missed; if it is set too low, too many false peaks will be introduced.

[0068] As a further improvement to the threshold search method, a sliding window can be set, where a fixed-size window slides across the signal, and the maximum value within each window is identified as a candidate peak point. This method can effectively smooth local fluctuations in the signal and reduce noise interference in peak search. Moreover, the window size can be flexibly adjusted according to the characteristics of the signal, exhibiting good adaptability. However, the limitation of this method lies in the need for careful selection of the window size; if the window is too large, it may mask some smaller peaks; if the window is too small, it may fail to effectively suppress noise.

[0069] The derivative method calculates the first derivative of a signal; the point where the derivative changes from positive to negative is the peak point. This method determines peaks based on the rate of change of the signal and can accurately capture abrupt changes in the signal. However, the derivative method is sensitive to noise. In noisy signals, the calculation of the derivative may introduce significant errors, affecting the accuracy of peak search. In practical applications, it is necessary to first perform sufficient smoothing filtering on the signal before using the derivative method for peak identification.

[0070] S123. Determine whether there are two T-wave candidate points. If so, take the lowest point between the two T-wave candidate points as the T-wave end point. If not, determine the T-wave end point based on the T-wave candidate points.

[0071] In some healthy hearts, a U wave appears after the T wave ends, such as in healthy adolescents and young adults. Whether using the threshold method or the derivative method, the presence of the U wave will cause two peaks (i.e., T wave candidate points) to be detected when detecting the peak value of the T wave within the RR interval. This will affect the judgment of the end time of the heart contraction, so this situation needs to be excluded.

[0072] When a U wave is present in an electrical signal, the trough between the U wave and the T wave can be used as the end point of the T wave to indicate the end of the cardiac mechanical contraction.

[0073] S124. Use the image data corresponding to the end point of the T wave as a candidate image for calculation.

[0074] When acquiring cardiac image data (such as MRI images), because the heart is constantly beating, the exposure time for each frame is very short to ensure image clarity. This results in each frame containing very limited effective information. Therefore, it is necessary to merge multiple frames of the heart under the same condition obtained from multiple exposures to obtain a clear image of the heart in that state. Thus, the above steps can filter image data for each RR interval to obtain multiple candidate computational images for multiple RR intervals. These images are then merged to form a complete and clear cardiac image, which is then segmented and registered to establish a three-dimensional cardiac model.

[0075] Specifically, the candidate computational images can be segmented and registered to establish a three-dimensional model of the heart through the following steps:

[0076] S131. Use image segmentation algorithms (such as threshold-based segmentation, edge-based segmentation, or region-based segmentation) to accurately separate the heart region from the background in the candidate computational image.

[0077] The purpose of this step is to remove irrelevant information and retain only image data related to the heart for subsequent processing. Simultaneously, the quality of the segmented heart region should be evaluated. If the segmentation result is unsatisfactory, the parameters of the segmentation algorithm can be adjusted or other segmentation methods can be used for re-segmentation.

[0078] S132. Extract features from the segmented heart region image, extract key features of the heart such as the heart outline, myocardial thickness, and ventricular cavity size, and build a SIFT descriptor for each key feature;

[0079] There are various feature extraction methods, but the most widely used is the deep learning-based method. This method utilizes convolutional neural networks (CNNs) to train on a large amount of cardiac image data, allowing the network to automatically learn the feature representation of the heart. CNNs can capture complex features and patterns in images and have strong generalization ability, accurately extracting key features from cardiac images of different individuals and under different imaging conditions.

[0080] SIFT descriptors are highly invariant to image rotation, scaling, and brightness changes, enabling accurate matching of key feature points under different viewing angles and lighting conditions. In cardiac image registration, SIFT descriptors can effectively address the potential differences in the heart's position, angle, and scale across different images. By calculating the similarity between SIFT descriptors of key feature points in different images, corresponding points can be found quickly and accurately, thus achieving precise image registration.

[0081] S133. Perform translation transformation on the image data based on the SIFT descriptors of key feature points, and generate a three-dimensional mask model of the heart through image registration.

[0082] The registered 3D mask model forms a mesh composed of multiple tiny cubes. Each vertex of the cube corresponds to a mask value of an image pixel (i.e., the label value after feature extraction, such as "1" for myocardium and "0" for background). It accurately describes the surface of the structure segmented from the image data, but usually contains a lot of jagged edges and noise.

[0083] S134. Smooth the three-dimensional mask model to eliminate the jagged (stepped) appearance caused by image voxel resolution and segmentation error, restore the smoothness of the heart surface, and form a three-dimensional heart model.

[0084] There are various methods for smoothing, including Laplace smoothing, Taubin smoothing, and anisotropic filtering. These methods are existing technologies and will not be elaborated here.

[0085] After obtaining the three-dimensional model of the heart, medical staff mark the locations where electrodes 2 need to be installed on the three-dimensional model of the heart, and design the shape of electrode wires 21 and flexible substrate 1 according to the locations of electrodes 2, thus establishing a three-dimensional model of the calibration electrodes. This step can be carried out manually by medical staff or by an automated program, and specifically includes the following steps:

[0086] S31. Establish a global coordinate system, obtain the coordinates of each electrode 2 in the global coordinate system, and the coordinates of the outer contour of the heart 3D model in the global coordinate system;

[0087] S32. Establish a wiring mesh on the outer contour of the heart 3D model, and use a path search algorithm to automatically generate an electrode wire model based on the coordinates of each electrode 2 and the electrode wire wiring rules.

[0088] The electrode wire routing rules include: the width of the electrode wire 21 is 10-300μm, the distance between two adjacent electrode wires 21 is 200μm-2cm, and each electrode wire 21 cannot cross each other. The electrode wire 21 eventually extends to the common part 12 and is finally connected to the communication interface 4 through the bus part 13.

[0089] There are several methods for automatically creating electrode wires, such as the A-search algorithm and the Steiner tree algorithm, which can automatically find the optimal path along the mesh according to the electrode wire routing rules. This application uses the Steiner tree algorithm to automatically create the electrode wire model. The specific steps are as follows:

[0090] S321. Create electrode nodes on the wiring mesh according to the position of electrode 2, and create a set of communication interface nodes;

[0091] S322. Using the Steiner tree algorithm, based on the determined set of electrode nodes and communication interface nodes, construct a tree structure connecting all electrode nodes and communication interface nodes. Continuously adjust the wiring grid nodes traversed by each branch to ensure that each branch satisfies the electrode wire wiring rules. The resulting wiring diagram is as follows: Figure 7 As shown;

[0092] S323. Smooth the branches connecting each electrode node and communication interface node, and check whether the smoothed branches meet the electrode wire routing rules. Adjust the branches that do not meet the electrode wire routing rules.

[0093] S324. Create an electrode wire model based on the tree structure according to the size of each electrode 2 and the size of the electrode wire 21.

[0094] The Steiner tree algorithm can form an ideal communication interface 4 node, which automatically generates a bus structure to gather multiple electrode wires 21 into a "trunk" that meets the electrode wire wiring rules, thereby forming a bus section 13 with a regular shape, and connecting the bus section 13 to the communication interface 4 to create an electrode wire model with wiring rules.

[0095] S33. Based on the preset electrode 2 dimensions and electrode wire model, create a three-dimensional surface model of the flexible substrate 1 to obtain the three-dimensional model of the calibration electrode.

[0096] In particular, since the three-dimensional model of the calibration electrode needs to be unfolded into a two-dimensional graphic in the subsequent steps, the constructed three-dimensional curved surface model needs to be an unfoldable curved surface, such as a cylindrical surface or a conical surface. Therefore, in step S33, the center line of the branch 11 can be created first according to the electrode wire 21 model, and the curved surface can be generated by scanning along the center line according to the preset width of each branch 11 (e.g., 100μm-3cm as mentioned above).

[0097] When the three-dimensional model of the calibration electrode is a developable curved surface, it can be directly unfolded into a two-dimensional graphic through coordinate transformation. This method is widely used in many existing CAD software programs and is considered existing technology, so it will not be elaborated on here.

[0098] The above method can accurately construct a three-dimensional model of the heart in the contraction state, and prepare matching mapping electrodes based on the three-dimensional model, thereby ensuring that each electrode 2 can be located in the expected position after the mapping electrodes are attached to the heart, and improving the reliability of the obtained cardiac electrophysiological signals.

[0099] Example 2

[0100] When transporting an ex vivo heart, it is stored in a plastic isolation bag filled with bodily fluids. As a result, not only will the flexible substrate of the mapping electrode and the heart form liquid adsorption, but the outer encapsulation layer and the isolation bag will also have liquid adsorption. When the heart is beating, electrode 2 may detach from the heart.

[0101] Therefore, this embodiment improves the calibration electrode provided in Embodiment 1, referring to... Figure 8The flexible substrate 1 also includes an annular fastening portion 14, with the free end of each branch 11 connected to the annular fastening portion 14, forming a net-like structure for the entire mapping electrode. The diameter of the annular fastening portion 14 is slightly smaller than the diameter of the heart in a contracted state. When the annular fastening portion 14 is fitted onto the heart, it can achieve relative fixation with the heart, thereby fixing the relative position of all branches 11 to the heart and ensuring good contact between each electrode 2 and the heart.

[0102] Furthermore, for ease of preparation and use, the annular fastening part 14 is provided with a notch, and a connecting hole 15 is provided at both ends of the notch. A connecting pin 16 is also provided. When the connecting holes 15 on both sides of the notch overlap, the two ends of the notch can be fixed together by the connecting pin 16, thereby facilitating the use of the motor for calibration.

[0103] The connecting pin 16 can be made of medical-grade silicone, whose softness and non-toxicity ensure that it will not cause biotoxicity to cells during short-term contact with the heart. The shape of the connecting pin 16 can be referenced. Figure 8 As shown, it includes a disc head 161 and a fixing pin 162. The diameter of the end of the fixing pin 162 near the disc head 161 is smaller than that of the end away from the disc head 161, and the diameter of the end of the fixing pin 162 away from the disc head 161 is slightly larger than the diameter of the connecting hole 15, so that the connecting pin 16 can realize the function of fixing the two ends of the notch of the annular fastening part 14.

[0104] To better fit the shape of the heart, the mapping electrode in this embodiment should have a three-dimensional shape. Therefore, its preparation process differs from that of the mapping electrode in Embodiment 1. The mapping electrode is not included in the preparation process of the annular fastening part 14. After the mapping electrode without the annular fastening part 14 is cut and released, the annular fastening part 14 is made by transfer printing. Specifically, the following steps are included:

[0105] 7. Create a 3D mold of the heart based on the 3D model of the heart. The 3D mold of the heart can be a hollow shell with only the outer outline of the heart, and can be made by 3D printing.

[0106] 8. Place the mapping electrode (excluding the annular fastener 14) onto the three-dimensional heart mold, so that the electrode 2 is in contact with the three-dimensional heart mold. This can be done by spraying a small amount of pure water onto the three-dimensional heart mold and using the surface tension of the water to make the mapping electrode adhere to the three-dimensional heart mold.

[0107] 9. Based on the three-dimensional model of the calibration electrode, spin-coat PDMS solution onto the area where the annular fastening part 14 is located on the three-dimensional mold of the heart. Heat the three-dimensional mold of the heart at a temperature of 65-80℃ to solidify the PDMS. Then cool it to room temperature to complete the preparation of the annular fastening part 14.

[0108] Furthermore, after preparing the annular fastener 14, the annular fastener 14 can be cut open with scissors to form a notch, and then connection holes 15 can be opened at both ends to facilitate the use of the calibration electrode.

[0109] The cross-section and diameter of the annular fastener 14 need to be coordinated with the dimensions of the branch 11, while also taking into account the specific dimensions of the heart.

[0110] refer to Figure 9 The dashed line in the figure represents the shape of the heart after diastole. Its longitudinal (i.e., the direction of branch 11's extension) and transverse (circumferential) shapes are simplified to circles, with a longitudinal radius of R2 and a transverse diameter of D2. The solid line represents the shape of the heart during contraction, with a longitudinal radius of R1 and a transverse diameter of D1. When the annular fastener 14 can remain relatively stationary with respect to the heart, the heart's expansion from contraction to diastole will stretch branch 11 along its length. Due to the constraint of the common portion 12 of the flexible substrate 1 (for simplified calculation, it is assumed that the common portion 12 and the heart do not undergo relative displacement), the stress generated by the stretching of branch 11 will be applied to the annular fastener 14. Therefore, the frictional force between the annular fastener 14 and the heart is required. Greater than the tensile force generated when branch 11 is stretched ,Right now:

[0111]

[0112] In the formula, n is the number of branches 11.

[0113] friction The calculation formula is as follows:

[0114]

[0115] In the formula, The coefficient of friction between the annular fastener 14 and the heart is given. When the flexible substrate 1 is fabricated using PDMS, the coefficient of friction is... between, The pressure exerted on the heart by the annular fastener 14 due to diastole is calculated as follows:

[0116]

[0117] In the formula, The original width of the annular fastener 14. The original circumference of the annular fastener 14. The elastic modulus of the material of the annular fastener 14 is 0.4-2 MPa for PDMS. The strain of the annular fastener 14 is calculated as follows:

[0118]

[0119] The elastic modulus of the material is given by ρ, which is 0.4-2 MPa for PDMS.

[0120] Tension of branch 11 It can be calculated using the following formula:

[0121]

[0122] In the formula, For the width of branch 11, For the thickness of branch 11, The elastic modulus of branch 11 is used because the elastic modulus of the electrode wire 21 attached to branch 11 (whether Au or Pt) is much greater than that of PDMS. For example, the elastic modulus of Au is 79 GPa. Therefore, the elastic modulus of the electrode wire 21 is used. The strain produced by the stretching of the branch is calculated using the following formula:

[0123]

[0124] In the formula, The original length of branch 11, Let be the length of branch 11 after it is stretched. When there is no relative sliding between the annular fastener 14 and the heart, the longitudinal angle of the heart covered by branch 11 can be considered constant. Therefore, its strain before and after the change can be calculated according to the radius of the heart, that is:

[0125]

[0126] In summary, the dimensional relationship between the annular fastener 14 and the branch 11 can be described as follows:

[0127]

[0128] As can be seen, the dimensions of the annular fastener 14 and the branch 11 need to take into account not only their own dimensional relationship, but also the size relationship of the heart. Therefore, when preparing the mapping electrode described in this application, it is necessary to adapt it to the size of the patient's heart.

[0129] Based on the above analysis, after obtaining the three-dimensional model of the mapping electrode, a cardiac mathematical model and a mapping electrode mathematical model were established. The three-dimensional model of the mapping electrode was then optimized through dynamic coupling analysis of the two models. (Refer to...) Figure 10 Specifically, it includes the following steps:

[0130] S5. Acquire image data of the heart and establish a three-dimensional model of the heart at the end of diastole;

[0131] The specific process is the same as establishing a three-dimensional model of the heart at the end of contraction.

[0132] S6. Establish dynamic mathematical models of the heart based on the three-dimensional models of the heart at the end of diastole and the end of systole, respectively, including the contour features of the heart when systole is at its minimum state and the contour features when diastole is at its maximum state.

[0133] S7. Establish a finite element model of the calibration electrode based on the three-dimensional model of the calibration electrode, which can reflect the geometric characteristics and material mechanical properties of calibration electrode 2;

[0134] S8. Perform dynamic coupling analysis between the cardiac dynamic mathematical model and the finite element model of the mapping electrode to simulate the interaction between the mapping electrode and the heart under different contraction and relaxation states of the heart, and obtain the contact stress and relative displacement between the mapping electrode and the heart.

[0135] S9. Using zero relative displacement as a constraint, establish the objective function with minimum contact stress, and use the constraint optimization method to optimize the contact stress between the electrode mapping and the heart. Optimize the three-dimensional model of the mapping electrode, optimize the width and thickness of each branch 11 of the mapping electrode, and output the final three-dimensional model of the mapping electrode.

[0136] A dynamic coupling analysis was performed between the cardiac dynamic mathematical model and the mapping electrode mathematical model. This coupling analysis yielded data on the mechanical response, displacement changes, and stress distribution of the mapping electrode in the dynamic cardiac environment. Based on these analysis results, the structural parameters of the three-dimensional model of the mapping electrode were adjusted and optimized to minimize the contact stress between the mapping electrode and the heart while ensuring good contact between electrode 2 and the heart. This reduced the pressure exerted by the mapping electrode on the heart and decreased the risk of cardiac damage.

[0137] Example 3

[0138] The mapping electrode provided in Embodiment 2 uses a connecting pin to connect the annular fastening part to hold the heart tightly. However, the connecting pin 16 will form a small protrusion inside the annular fastening part, which poses a risk of damage to the heart during long-term transportation.

[0139] Further improvements were made to the calibration electrode provided in Example 1, with reference to... Figure 11 The flexible substrate 1 also includes multiple connecting parts 17 that intersect with the branches 11. The multiple connecting parts 17 and the multiple branches 11 intersect to form a grid-like structure that is connected end to end, which can achieve the wrapping of the heart, thereby ensuring that the electrodes set at the connection positions of the connecting parts 17 and the branches 11 can always have good contact with the heart.

[0140] The electrode wires 21 can be laid along the branch 11 or the connecting part 17, or they can be led out directly from each electrode 2 and set independently.

[0141] The flexible substrate 1 and the encapsulation layer 3 are made of PDMS material, and PEDOTPSS is used as the electrode wire 21, so that the entire mapping electrode has good deformation ability. Each branch 11 and the connection part 17 can stretch or contract with the heartbeat, thereby reducing the pressure of the mapping electrode on the heart and reducing the risk of heart damage.

[0142] Furthermore, in order to integrally form the three-dimensional mapping electrode using the screen printing process, the mapping electrode needs to be fabricated through two screen printing processes. The specific process is as follows:

[0143] 1) Print the encapsulation layer according to the encapsulation layer stencil;

[0144] 2) Print electrodes and electrode wires using an electrode stencil;

[0145] 3) Printing flexible substrates using a substrate stencil;

[0146] 4) Apply a sacrificial layer;

[0147] 5) Print the flexible substrate again using the substrate stencil;

[0148] 6) Print electrodes and electrode wires again using the electrode stencil;

[0149] 7) The encapsulation layer is printed again using the encapsulation layer stencil, so that the connecting portion 17 and the branch 11 of the two printed flexible substrates can be connected to each other at the ends, such as... Figure 12 As shown;

[0150] 8) Clean and remove the sacrificial layer (PMMA, polymethyl methacrylate, removed with acetone solution), peel off the standard electrode, and complete the preparation.

[0151] The above steps allow for the formation of a one-piece mesh-shaped measuring electrode using screen printing technology, with a cross-sectional structure as shown below. Figure 12 As shown.

[0152] It is important to note that when creating a three-dimensional model of the heart, it is necessary to identify the coronary arteries. When creating the three-dimensional model of the mapping electrodes, the connector 17 and branch 11 should be kept away from the coronary arteries to avoid compressing the coronary arteries and causing insufficient blood supply to the heart.

[0153] During the process of unfolding the mapping electrode from a three-dimensional model into a two-dimensional graphic, since the surface of the heart is a three-dimensional curved surface that cannot be unfolded, it is impossible to obtain an accurate two-dimensional unfolded pattern of the mapping electrode. Only an approximate value can be obtained. The specific unfolding process can be carried out using finite element algorithms (such as isometric mapping or common mapping) based on the principle of energy minimization. This can keep the local angles or area ratios unchanged and obtain an approximate two-dimensional unfolded result of the three-dimensional model of the mapping electrode, i.e., the electrode pattern. Finite element algorithms such as isometric mapping or common mapping are existing technologies and will not be elaborated here.

[0154] Furthermore, during the preparation of the mapping electrode, PEG gel and PEDOTPSS can be coated on the surface of electrode 2 that contacts the heart to enhance the contact stability between electrode 2 and the heart.

[0155] Further, refer to Figure 11 A fastening pull ring 18 can also be installed on each branch near the apex of the heart and the superior vena cava (or aorta). By inserting a tension rope inside the fastening pull ring 18, the adhesion effect of the mapping electrode to the heart can be improved, ensuring that the mapping electrode does not move relative to the heart during transportation and ensuring the reliability of the electrical signal measured by the mapping electrode.

[0156] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A flexible multi-channel cardiac mapping electrode for cardiac transport, characterized in that, include: A flexible substrate having multiple branches, with the fixed ends of all branches connected to a common portion, the flexible substrate being made of a biocompatible flexible insulating material, so that each branch can be adsorbed by the surface tension of bodily fluids on the outer surface of the heart; Multiple electrodes are arrayed on the side of each branch that contacts the heart to measure the heart's potential. Each electrode is provided with an electrode wire that penetrates the flexible substrate and extends along the side of the flexible substrate away from the measuring electrode to the common part, and finally connects to the communication interface. An encapsulation layer is disposed on the side of the flexible substrate facing away from the electrode and covers the electrode wires for encapsulating the electrode wires. The preparation steps of the calibration electrode include: Acquire image data of the heart and build a three-dimensional model of the heart at the end of contraction; Specify at least one electrode location on the three-dimensional model of the heart; Based on the electrode positions, electrode wires and flexible substrates are designed to form a three-dimensional model of the calibration electrode. The three-dimensional model of the calibration electrode is unfolded into a two-dimensional planar graphic to form an electrode pattern; The calibration electrode is prepared according to the electrode pattern.

2. The calibration electrode according to claim 1, characterized in that, Each branch has a width of 100μm-3cm and a thickness of 5-200μm. Each electrode and electrode wire has a thickness of 10-300μm and a width of 10-300μm. The spacing between two adjacent electrode wires is 200μm-2cm.

3. The calibration electrode according to claim 1, characterized in that, The flexible substrate further includes an annular fastening part, the free end of each branch is connected to the annular fastening part, the annular fastening part is provided with a notch, and both ends of the notch are provided with connection holes; The calibration electrode also includes a connecting pin, which is used to fix the two ends of the notch together after the connecting holes on both sides of the notch overlap.

4. The calibration electrode according to claim 1, characterized in that, The flexible substrate further includes a plurality of connection portions that intersect and connect with the branches, and the electrodes are disposed at the connection portions and the branch connections; The plurality of connecting portions and the plurality of branches form a loop that can surround the heart to enclose the heart and keep the electrodes in contact with the heart.

5. The calibration electrode according to any one of claims 1-4, characterized in that, The flexible substrate and the encapsulation layer are made of PDMS, PI or PU, and the electrode wires are made of PEDOTPSS, platinum carbon or conductive silver paste. The side of the flexible substrate that contacts the heart is treated with a hydrophilic coating.

6. A method for constructing a mapping electrode, used to construct the mapping electrode according to any one of claims 1-4, characterized in that, Includes the following steps: Acquire image data of the heart and build a three-dimensional model of the heart at the end of contraction; Specify at least one electrode location on the three-dimensional model of the heart; Based on the electrode positions, electrode wires and flexible substrates are designed to form a three-dimensional model of the calibration electrode. The three-dimensional model of the calibration electrode is unfolded into a two-dimensional planar graphic to form an electrode pattern; The calibration electrode is prepared according to the electrode pattern.

7. The method according to claim 6, characterized in that, The three-dimensional model of the heart is established through the following steps: Simultaneously acquire image data and physiological electrical signals of the heart; Peak and trough values ​​are filtered based on the physiological electrical signals to identify the heart's pulsation cycle, and image data of the heart in a contracted state are selected as candidate images for calculation. The candidate computational images are segmented and registered using a deep learning algorithm to establish the three-dimensional model of the heart.

8. The method according to claim 7, characterized in that, The candidate computational image is obtained through the following steps: Identify the RR interval in physiological electrical signals; Search for peak points other than the R peak during the RR interval as candidate points for the T wave; Determine if there are two candidate points for the T-wave. If so, take the lowest point between the two candidate points as the end point of the T-wave. If not, determine the end point of the T-wave based on the candidate points. The image data corresponding to the T-wave termination point is used as a candidate image for calculation.

9. The method according to claim 7, characterized in that, The candidate computed image is segmented and registered using the following steps: The heart region in the candidate computational image is separated using an image segmentation algorithm; Feature extraction is performed on the image of the heart region to obtain key features of the heart, and a SIFT descriptor is built for each key feature; The image data is translated and transformed based on the SIFT descriptor to generate a three-dimensional mask model of the heart. The three-dimensional mask model is smoothed to form the three-dimensional model of the heart.

10. The method according to claim 6, characterized in that, The three-dimensional model of the calibration electrode is obtained through the following steps: Establish a global coordinate system, obtain the coordinates of each electrode in the global coordinate system, and obtain the coordinates of the outer contour of the three-dimensional heart model in the global coordinate system; A wiring mesh is established on the outer contour of the heart 3D model. An electrode wire model is created based on the coordinates of each electrode and the electrode wire wiring rules using a path search algorithm. A three-dimensional surface model of the flexible substrate is created based on the electrode dimensions and the electrode wire model to obtain the three-dimensional model of the calibration electrode.

11. The method according to claim 6, characterized in that, The method further includes the following steps: Acquire image data of the heart and build a three-dimensional model of the heart at the end of diastole; A dynamic mathematical model of the heart was established based on the three-dimensional model of the heart at the end of diastole and the three-dimensional model of the heart at the end of systole, respectively. A finite element model of the calibration electrode is established based on the three-dimensional model of the calibration electrode. The dynamic mathematical model of the heart and the finite element model of the calibration electrode are subjected to dynamic coupling analysis to simulate the interaction between the calibration electrode and the heart under different contraction and relaxation states of the heart, and to obtain the contact stress and relative displacement between the calibration electrode and the heart. Using zero relative displacement as a constraint and minimum contact stress as the objective function, the three-dimensional model of the calibration electrode is optimized. The width and thickness of each branch of the calibration electrode are optimized, and the final three-dimensional model of the calibration electrode is output.

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